You’re
a regular in the gym’s weight room, grunting and sweating in
hopes of turning fat into muscle and maybe even losing some
weight. And yet your goal eludes you.

New
research on women finds that some are resistant to resistance
training. For these women, the new study suggests, a welter of
genetic variations protect their bodies from fat loss and
prime their bodies to maintain their weight, even in the face
of heroic body-sculpting efforts.

In
short, however hard these women work to shape up with
resistance exercise, their fat genes seem to work harder to
thwart their efforts.

Among
the study’s 148 women between 35 and 60, those who carried
few of the 21 genetic risk variants for obesity that
researchers measured largely responded to a regimen of weekly
resistance exercise by losing weight, trimming fat —
especially abdominal fat — and shifting their overall body
composition in a leaner direction.

The more
of those 21 genetic variants a woman had, the less likely she
was to see any of these changes, even if she was a
conscientious participant in the three 75-minute
resistance-training sessions that researchers asked subjects
to attend each week for one year.

These
findings underscore the limits of even intensive physical
activity in reducing the risks of people whose genes
predispose them to certain health conditions. Other studies
have found that for people at elevated genetic risk of Type 2
diabetes and of worrisome cholesterol, exercise regimens
designed to reduce those risks were less effective in doing so
than they were for people whose genes did not spell trouble.

After a
year, women in the exercise arm of the trial were clearly
trimmer and in better shape, overall, than women who did not
get the exercise intervention. But those averages hid the
struggles of women at high genetic risk for obesity, who were
working hard and not getting the hoped-for results.

The
average age of subjects in the current study was 56, and in
enrolling participants, researchers requested that the women
make no efforts to change their diet or body weight during the
study, or either start or discontinue hormone-replacement
therapy. The muscle strength of women assigned to the study’s
resistance-exercise arm was tested every six to eight weeks to
ensure they were increasing the loads they bore and
maintaining the intensity of their exercise as they became
more fit.

Of the
32 genetic variations that have been linked to obesity in
humans, the study’s authors tested each woman for 21 genetic
variants. They weighted the genetic variations according to
how strongly they have been found to influence obesity, ranked
each woman on how many or few of those alleles she carried,
and divided the women into low-, intermediate- and high-risk
groups.

Researchers
found no evidence that any one of the obesity-related 21
genetic variants they measured was more decisive than another
in reducing the positive effects of resistance training.
Instead, they suggested, the grab-bag of obesity-related genes
appeared to work together to thwart a woman’s success. While
exercise might work to reduce appetite and turn up the
calorie-burning thermostat of a woman with few obesity genes,
the women with many appeared to compensate for their work in
the gym with increased appetites, more efficient
calorie-burning and other physiological measures that
protected their fat stores and prevented weight loss.

In fact,
while women who had low- and intermediate-levels of
obesity-related genetic variants lost weight and fat mass and
increased their lean mass, women with the highest levels of
those variants gained weight and lean mass, while their fat
mass stayed steady.